Apparatus for manufacturing high pressure inert gas

ABSTRACT

THIS INVENTION RELATES TO AN APPARATUS FOR MANUFACTURING HIGH PRESSURE INERT GAS UTILIZING HYDROCARBON FUEL, THE GAS BEING PRODUCTED BY THE BURNING OF HYDROCARBON FUEL IN AN INTERNAL COMBUSTION ENGINE, THE EXHAUST GASES THEREFROM BEING CONVEYED THROUGH A CATALYTIC CONVERTER WHEREBY SUBSTANTIALLY INERT GAS A DERIVED THEREFROM, AND INCLUDING MEANS OF CONTROLLABLY RECYCLING SUCH INERT GAS THROUGH ENGINE DRIVEN COMPRESSOR STAGES TO VARY THE LOADING ON THE ENGINE AND THEREBY VARY THE INERT GAS OUTPUT IN RESPONSE TO THE DEMAND. AN ADDITIONAL EMBODIMENT OF THE INVENTION INCLUDES MEANS TO MAINTAIN A POSTIVE PRESSURE IN ALL PORTIONS OF THE SYSTEM, INCLUDING THE ENGINE ENHAUST MANIFOLD AND CATALYTIC CONVERTER, SO THAT ANY INADVERTENT LEAK IN THE SYSTEM WILL NOT RESULT IN AIR BEING DRAWN INTO THE SYSTEM.

G. H. csowERl May 18, 1.971

APPARATUS FOR MANUFACTURING HIGH PRESSURE INERT GAS Filed sept. 25. 1969 /A/VE/vrof? GEORGE H. GwER ATTORNEYS United States Patent O 3,579,308 APPARATUS FOR MANUFACTURING HIGH PRESSURE INERT GAS George H. Gower, Tulsa, Okla., assignor to Inert Gas Corporation, Tulsa, Okla. Filed Sept. 25, 1969, Ser. No. 860,908 Int. Cl. B015 7 /00 U.S. Cl. 23-281 5 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an apparatus for manufacturing high pressure inert gas utilizing hydrocarbon fuel, the gas being produced by the burning of hydrocarbon fuel in an internal combustion engine, the exhaust gases therefrom being conveyed through a catalytic converter whereby substantially inert gas is derived therefrom, and including means of controllably recycling such inert gas through engine driven compressor stages to vary the loading on the engine and thereby vary the inert gas output in response to the demand.

An additional embodiment of the invention includes means to maintain a positive pressure in all portions of the system, including the engine exhaust manifold and catalytic converter, so that any inadvertent leak in the system will not result in air being drawn into the system.

BACKGROUND AND OBJECTS OF THE INVENTION A variety of systems and processes utilized in industry require inert gas. At the present time, one of the biggest usages of inert gas is in the petroleum industry wherein such gas is utilized in the recovery of petroleum products. In many instances subterranean oil reservoirs are lacking in sufficient self-stored uid or gas pressure to cause movement of the crude oil out of the formation and into boreholes where it can be pumped to the surface. A well known method of augmenting natural reservoirs dynamics is to inject gas under pressure into the reservoir, the gas serving to drive the petroleum product through the formation into well boreholes wherein the product can be pumped to the surface. y n

Gas utilized for such purposes must be inert. That is; it must be substantially free from oxygen to avoid creati ing explosion hazards and to minimize corrosion of equipment. In addition, such gas must be virtually free of acid forming components. It is understood that the term inert gas as used herein does not mean that the gas has to be completely inert in the sense that pure helium is inert, but it must be substantially lacking in oxygen and acid forming components.

An efcient and effective means of producing such inert gas includes burning hydrocarbon fuel in an internal combustion engine, utilizing the exhaust gas as a raw material from which the inert gas is produced. The exhaust gas is treated by reaction in a catalytic converter which removes the unwanted components. The product passing out of the catalytic converter must normally then be compressed prior to injection into subterranean crude oil bearing formations. The compressors necessary to compress the inert gas are normally driven by the internal combustion engine itself so that the energy consumed in producing the inert gas is effectively utilized.

One problem which exists is that it is necessary, or at least highly desirable, in most installations, to maintain a substantially constant inert gas output pressure as the "ice demand varies. Various factors cause the demand for the inert gas to change, such as changes in ambient temperature, atmospheric pressure, amount of product taken from wells extending into the formation, and so forth. It is therefore an object of this invention to provide an apparatus for manufacturing high pressure inert gas utiliz-- ing hydrocarbon fuel, including means of maintaining substantially constant inert gas pressure output as the demand varies.

Another object of this invention is to provide an apparatus for manufacturing high pressure inert gas including an internal combustion engine and a plurality of compressors driven by the internal combustion engine for increasing the pressure of the inert gas produced, including means of recycling gas through compressor stages as a means of varying the loading of the internal combustion engine to thereby vary and regulate the quantity of the inert gas produced.

Another object of the invention is to prevent the occurrence of a vacuum anywhere in the system, and especially in the piping system before and after the catalytic converter.

These, as well as other objects of the invention, will be understood from the description and claims taken in conjunction with the drawings.

DESCRIPTION OF THE DRAWINGS The drawing is a schematic diagram showing an arrangement of apparatus including means for automatically regulating the quantity of inert gas produced.

DETAILED DESCRIPTION Referring to the drawings, exhaust gas is produced by an internal combustion engine 10. The engine 10 is fueled by hydrocarbon fuel passing to the engine through line 12 and control valve 14 to the engine intake 16. The exhaust 18 of engine 10 is fed to a catalytic converter 20 wherein corrosive and other components are converted by chemical reaction in the presence of a catalyst into non-corrosive components. The outlet 22 from the catalytic converter 20 provides substantially inert gas at a low pressure.

In order for the inert gas produced at outlet 22 of catalytic converter 20 to be effectively utilized, and particularly for the purpose of injection into subterranean formations, the pressure of the gas must Ibe substantially increased. The inert gas is rst fed to a cooler 24 which is preferably powered by a fan 26 driven from crankshaft 28 of engine 10. In cooler 24 the inert gas is cooled and passed outwardly through cooler outlet 30 into a separator 32. Cooling of the gas results in the condensation of water vapor, and possibly other low vapor pressure components which should be moved before the gas is utilized for injection into a formation. The condensed water vapor is collected in separator 32 and passed out through drain valve 34. The inert gas, still under low pressure but cooled and having at least a portion of the water vapor extracted therefrom, passes out of the separator through outlet 35 and into the inlet of a compressor lirst stage 36 which is driven by the engine crankshaft 28. In the compressor rst stage 36 the inert gas is compressed and passes outwardly through outlet 38 into a cooler 40 and thence to a separator 32. Condensed water is taken out through drain valve 44. In the outlet 46 of separator 42 the inert gas has been raised in pressure and further water vapor has been removed.

In the typical utilization of the apparatus of this invention as a means of producing inert gas for a gas drive system to augment the production of petroleum more than one stage of compression is required to bring the inert gas up to the required pressure level. Thus the gas at outlet 46 is fed to a compressor second stage 50 wherein the pressure of the inert gas is again raised. The gas is passed from outlet 52 to cooler 54 and separator 56 wherein the steps of cooling and separating condensation are repeated as previously discussed, the condensation being discharged through drain valve 58. The outlet from separator l56 passes through line 60 to a compressor third stage 62 wherein the gas pressure is raised to the desired level at outlet `64 for usage for the intended purpose, the most frequent usage at the present time, as previously indicated, being for injection as a gas drive into a subterranean oil bearing formation.

The apparatus described up to this point may be said to be of a standard arrangement. Each of the compressor stages 36, 50 and l62 is driven from crankshaft 28 and in like manner, each of the fans 26, 66, and 68 is driven from crankshaft 28. Thus the engine performs the work of bringing inert gas produced from the fuel passing through inlet 12 up to the required pressure. A problem which exists with such known apparatus, however, is that changes occur in the demand for inert gas from time to time, changes being caused by factors such as seasonal or daily temperature changes, atmospheric pressure changes, and so forth. This invention provides means of self-regulating, within limited ranges, of the quantity of exhaust gas produced by engine 10.

A governor 70, responsive to the speed of engine 10, controls fuel valve 14, so as to maintain the engine 10 at substantially a preselected speed of rotation. Thus, as long as the work load on engine 10 is the same, the quantity of exhaust gas, and therefore inert gas, produced remains the same. However, by varying the work load on the engine 10, while maintaining the speed of rotation at substantially the same level, the quantity of exhaust gas produced and thereby the quantity of inert gas produced, can be varied. This invention takes advantage of this fact.

A recycle conduit 72 connects with the output of the second stage separator 56 and, through pressure control valve 74 and conduit 76, passes recycled gas back through compressor second stage 50. With valve 74 open gas compressed in second stage 50 is passed through cooler 54, separator 56, outlet conduit 60, recycle conduit 72, and valve 74 back into the inlet of compressor second stage 50. This recycling of gas increases the load on engine 10 since the recycle gas, in each successive cycle of compression, absorbs energy in compression and releases the energy in cooler 54. When valve 74 is open then the cooler 54 discharges more heat than when valve 74 is closed. The increased thermal energy loss is reflected back as a power loss, tending to slow down engine 10. Governor 70, functioning to maintain the engine at a preselected speed of rotation, opens fuel valve 14, increasing the fuel inlet into the engine 10. As the fuel valve 14 is opened, the engine consumes more fuel and more exhaust gas is produced and passed through the catalytic converter and through the cascaded pressure and cooler stages. In this way, with valve 74 open, more fuel is consumed and therefore more exhaust gas, and consequently more inert gas, is produced.

Valve 74 is pressure controlled, the pressure being sensed through pipe 78 communicating with the outlet of separator 32. As the pressure of the inert gas falls such is reflected back through to the outlet of separator 32, which reduced pressure is conveyed by pipe 78 to the pressure control valve 74, causing the valve 74 to open. This causes, by arrangement previously described, the increased production of exhaust gas which continues until the supply equals the demand at which time Vale 74 will close. Thus the system is self-regulating to produce inert gas at a variable quantity in response to demand.

It can be seen that the range of demand is not extensive however, in any given installation of a gas drive system the required quantity and pressure of inert gas is carefully engineered in advance. In order to maintain a consistent quantity and thereby pressure of inert gas outlet,

4 only relatively small variations need be made in the system. According to this invention suchself-regulated control of the inert gas quantity output is obtained without expensive and elaborate control systems and by the utilizing of a single pressure control valve and a small quantity of piping.

In addition to controlling the quantity of inert gas produced it is also normally desirable to control the quality or chemical content. The chemical content of exhaust gas is regulated, for any given hydrocarbon fuel, by the fuel/air mixture consumed in the internal combustion engine. Air is supplied to engine 10 through conduit 80 and controlled by valve 82. The outlet 84 from valve 82 passes into the intake system of engine 10. Valve 82 is controlled in response to an exhaust gas analyzer 86 which samples gas taken from the outlet 22 of catalytic converter 20. Air valve 82 understandably is not a valve in the sense as utilized to control liquid but is a vane type valve such as typically functions as a choke in engine carburetors or valve 82 may be in the form of a controllable supercharger. By controlling fuel valve 14 and air valve 82 the apparatus of this invention provides a means of producing inert gas regulated both as to quantity and chemical content.

In this illustrated example of the application of this invention the arrangement is shown wherein engine 10 drives three cascaded stages of compression with stage number two being recycled as a means of controlling the load and thereby the inert gas production. It can be seen that the invention may be practiced using cascaded compressor systems of fewer or greater numbers of stages and that the recycling to control the loading of engine 10 may encompass one, two or more of such cascaded stages and may encompass stages other than the second or intermediate stage of any cascaded system.

An additional embodiment of the invention includes means to maintain a positive pressure in all portions of the system. The intake of compressor first stage 36 would normally tend to pull a vacuum on conduit 35. If this occurred a vacuum could be established in separator 32, conduit 30, cooler 24, conduit 22, catalytic converter 20 and engine exhaust manifold conduit 18. If a vacuum should exist in any of these areas, and if a leak should exist in any of these areas, air would be drawn into the system. Even a small amount of air is highly detrimental to the product of inert gas.

To maintain a positive pressure throughout the system a pressure return conduit 88 extends from the first stage separator outlet conduit 46 back to the compressor first stage inlet conduit 35. A pressure control valve 90 regulates flow of gas from the compressor first stage outlet to the inlet in response to the pressure in engine exhaust manifold outlet 18 as sensed by line 92.

Control valve 90 is regulated such that a predetermined pressure must exist in engine exhaust conduit 18 otherwise valve 90 is opened, allowing recycling of gas flow through the compressor first stage 36 so as to maintain at all times a positive pressure on compressor first stage inlet conduit 35. Pressure drop will naturally occur by the effect of gas flow through catalytic converter 20, cooler 24, separator 32, as well as through conduits 18, 22 and 30. The amount of pressure drop will be determined by sizing of the equipment and conduits. As an example the apparatus may be arranged to maintain a pressure of 12" of water column on engine exhaust conduit 18, 8" of water column on catalytic converter outlet conduit 22, 4 of water column in cooler outlet conduit 30, and 2 of water column in compressor first stage inlet conduit 35. Thus, when the pressure in engine exhaust manifold outlet conduit falls below l2 of water column such would be communicated by control line 92 to control valve 90 opening the same thereby permitting gas flow from the outlet of compressor first stage 36 back to the inlet conduit 35. This will raise the pressure in conduit 35 which will be reflected back to increase pressure in the separator 32, conduit 30, cooler 20, conduit 22, catalytic converter 22 and conduit 18 until the desired pressure in conduit 18 is attained (such as 12" of water column) at which time control valve 90 will close. In this way a positive pressure is always maintained in the whole system. If a leak develops gas may escape from the system, which will only affect the system efciency but will not result in the introduction of excess oxygen to vitiate the inertness of the gas produced by the system.

While the invention has been described with a great deal of particularity it is manifest that many changes may be made in the details of constr-uction and the arrangement of components without departing from the spirit and scope of this disclosure.

What is claimed: 15

1. An apparatus for manufacturing high pressure inert gas utilizing hydrocarbon fuel comprising:

an internal combustion engine having a fuel inlet connected to a source of hydrocarbon fuel, an output drive shaft, and an exhaust;

a catalytic converter having an inlet and an outlet, the inlet communicating with said engine exhaust, such converter serving to convert corrosive elements of the exhaust gas of said engine to form inert gas;

a plurality of compressor stages each having a gas inlet and outlet, the compressor stages being cascaded, the gas outlet of each proceeding stage being connected to the gas inlet of the succeeding stage, the inlet of the 'lirst compressor stage being connected to said catalytic converter outlet, each of the compressor stages having an input drive shaft connected to said engine output drive shaft;

a plurality of coolers each having a gas inlet and outlet,

2. An apparatus for manufacturing high pressure inert gas according to claim 1 including:

a gas recycle conduit connected to the gas outlet of one of said compressor stages and to the gas inlet of a proceeding compressor stage;

a controllable gas recycle valve in said gas recycle conduit operable to regulate the rate of recycled gas yflow through said conduit; and

means of controlling said gas recycle valve in response to inert gas demand to increase the gas recycle rate through said gas recycle conduit when the inert -gas demand increases and decreases the gas recycle rate when the inert gas demand decreases to thus vary the loading of said engine to thereby vary the inert gas output in response to the demand.

3. An apparatus for manufacturing high pressure inert gas according to claim 1 including:

a separator in series with each of said coolers, each of said separators including drain means for discharging condensation therefrom.

4. An apparatus for manufacturing high pressure inert gas according to claim 1 including:

a governor responsive to the speed of revolution of said engine drive shaft; and

a fuel gas valve in said inlet response to said governor whereby more fuel is passed to said engine as the speed of revolution of said drive shaft decreases and less fuel isY passed as the speed of revolution of said drive shaft increases.

5. An apparatus for manufacturing high pressure inert gas according to claim 1 wherein said gas has an air intake and including:

an air valve controlling the rate of air flowing to said one of said coolers being interposed between each of engine air intake; and

said cascaded compressor stages whereby the gas a combustion analyzer connected to sample and respond inlet of each such cooler is connected to the gas to the chemical composition of gas passing out of said outlet of a proceeding compressor stage and the gas catalytic converter outlet, said combustion analyzer outlet of such cooler is connected to the gas inlet including means connected to said air valve for conof the succeeding compressor stage; trolling the rate of air intake to said engine in repositive pressure gas recycle conduit connected to sponse to the chemical composition of gas passing out the gas outlet of one of said compressor stages and of said catalytic converter.

to said gas inlet of said rst compressor;

a controlled gas recycle valve in said positive Ipressure gas recycle conduit operable to regulate the rate of recycled gas flow through said conduit; and

References Cited UNITED STATES PATENTS 1,952,005 3/ 1934 Willenborg 23-281 means of controlling said gas recycle valve in said 2392711 1/1946 Wiuenborg 23 281 positive pressure gas recycle conduit in response to 3389972 ,6/1968 Pottharst Jr' 23 281 the pressure at said engine exhaust to increase the 3480199 11/1969 Bauer "417 253 gas recycle rate when the pressure at said engine exhaust falls below a predetermined pressure, to main- JAMES H. TAYMAN, JR., Primary Examiner tain a positive gas pressure in all parts of the apparatus to thereby prevent air being drawn into the U'S' C1- XR' 

